Xenosaga Episode I – Walkthrough

Complete Walkthrough

By Khdigifantasy13.

Kos Mos Simulation

  • Battle system tips:
    • In the bottom right corner is a reel that cycles every turn
      • Blank means no effect
      • Red flame means higher damage
      • Halo mean higher item drop rate
      • Coin + means a multiplier to the points it drops: Ep, TP, SP, Can be x2, x4, or even x10
    • Square attacks are physical, Triangle attacks are ether
    • Every attack requires 2 ap. To do Techs, you need to either only use 2 AP and stop, or guard for a turn.
    • Once you have enough TP later, you can go into the Tech menu and customize each.
      • Tech raises damage it does
      • Speed when maxed allows you to set to shorter command
      • Wait raises your turn order after using it.
      • Always focus on Speed first, then Wait, then Tech.
    • TP can also be used to raise stats in the Status screen to match the character with the highest. Always raise stats first before Tech damage level. Costs less and makes more of a difference
    • Shion comes with an accessory that lets you see enemy HP, it’s displayed in the SE corner at the turn gauge
  • Area is fairly straightforward, these beginning enemies drop HP items.
    • Don’t bother grinding here though, there’ll be a spot later 
  • Once you make your way inside and upstairs to the room will be a boss and the enemies will change.
    • The enemies now will drop EP restoring items instead of HP.
  • Make way to front of building and into the shutters for area boss

Woglinde

  • You can re-enter Kos Mos’ simulation by talking to the guy by her pod.
    • Return to where the last boss was to open the chest and exit
  • Continue forward to the Zohar room, in the bottom right corner talk to the man in orange right next to the opening to the exit room for emails
  • Continue forward and go straight to Shion’s room at the intersection
    • Examine the desk and go back
  • Left at the previous intersection for a scene
  • Go N out of the room and re-enter for mail, reply to it that you will help.
  • Go N till you get stopped by a driller.
    •  Will get a Med Kit S if you destroy everything on first try. Otherwise it’s just a med kit. Doesn’t matter either way because of what’s coming up.
  • In this next area, step into the left lounge for an email from Miyuki. Answer that you read it.
  • Go N again till you get stopped for a Decoder overview.
  • Continue NW to a game of tag, just run to a corner for them to move to a side and go around.
  • NW into the AGWS hanger, speak to the man in front of one in the back to participate in a simulation
    • Here you can grind against an AGWS. It’s not too hard, just us Ether attacks on it.
    • You will be healed after each fight and it will drop Med Kit S. Good place to grind out TP and SP
      • Start using your SP right away on your accessories to help start raising your S Lv for better accessories later
    • In the right sitting area is another man in orange that you can shop from. Sadly the AGWS don’t give money. You can sell the Med Kit S if you want, wait to buy anything though.
  • Once ready, head outside and right all the way around to the orange door up to the bridge and captain
    • Go back down for another email from Miyuki, download the plugin
    • Down the elevator, go E near the potted plants for an email, invest in Vector and pay 500 G.
  • Head to the AGWS hanger and talk to the man in green on the left side.
    • You can head back to Kos Mos room and around the border for another email
  • Return to Shion’s room and rest

Gnosis Attack

  • You have to  get into a fight with these first bunch.
    • From here, avoid the Gnosis at all cost, you cannot hurt them and they will kill you.
  • Right and close partition
  • NE and into the alcove to turn on a hologram
  • NW, ignore the room and attract the attention of the Gnosis on the left.
    • Once it’s following, retreat back into the room
  • Head left, up the ladder to the monitor in the middle
  • Back down the ladder, head SW to the man on the ground
  • Go to the AGWS room and speak to the vendor to unlock the Vaporizer Plugin
    • Outside, hide behind the box on the left to have the Gnosis destroy it, then run around so each get stuck on the yellow bars
  • Head S and, like the game of tag, draw the Gnosis out and around to avoid them
    • Enter the Decoder room for a part
  • Head SW to some scenes, examine the dead body for a key
    • Enter the nearby door for an AGWS weapon
  • Next side door has a save point, then head S to the Realian Bay for a boss, will counter with a heavy attack if hit with too many ether attacks.
    • After you gain access to Shion’s AWGS, equip the second SMG99AG. With both equip will allow W-ACT to be used in battle, a very strong tech for 6 AP. Though, you’ll still probably do more with Shion if you’ve increased her Ether Attack stat
  • Head E at the intersection and make you way N back to where you hid in a room with a chest behind glass for a Decoder 18 that unlocks the room by Shion’s room
    • If you go all the way back around to then N side of the broken bridge, there will also be a chest in some debris.
  • When you’re ready, head S from Shion’s room back to the Zohar and a boss

Pleroma

  • Head NE to the next room
    • You can fight enemies if you want, if you go for 6 AP you can use BMP55SX to attack all at once. Though this does use EP. 
    • This may sound crazy, but you’ll be better off focusing on Ether Attack than physical. Don’t invest TP in Cyber Kick
  • Continue E to the next room. 
  • In the NW corner, destroy the wall to get up to a chest with an accessory to prevent poison.
  • Back in the room, destroy the fixture in the middle for a Decoder 11
  • Continue right, use the crane in the SW to distract the AGWS to get to the next room.
  • SW to next room, then SE to a hall
    • W side has some items
    • E side has a mini-boss blocking the cell key
  • Go back and save Momo
    • If you want to keep Momo in the backrow, she won’t be able to attack with square or triangle. If you only want her for her Ether magics, then use the Ether Upgrade items on Ziggy to teach him Bodyguard. This will increase his attack and defense, as long as Momo is behind him.
    • Don’t go for Recharge right now, you can transfer Momo’s Life Shot to Ziggy for the same effect at half the EP to use. 
    • If you’re attacking with Momo, she does not have a tech for T+T, you’ll also want to switch her techs to only Floral Tempest, it’s stronger because it’s ether based instead of physical.
    • Focusing on Ziggy’s Ether Attack will let you deal massive damage with his “All Enemies” tech he learns at lv 15 later
      • Almost everybody in the game is better off focusing on Ether than Physical, except for one that will be stated later. Almost all “All Enemies” techs are ether based.
    • Return and defeat the AGWS we distracted to receive Decoder 4
  • Head back to where the cell key was and examine the monitor
  • Head SW down the ladder, head W, can visit the church for another Ether Upgrade.
    • The sewers is a decent place to level as the flying bots have low HP that even Momo can kill in one turn. Downside is they don’t really give much TP
  • When you’re ready, head up the W ladder for a boss with 3 AGWS
    • Use Momo’s Sheep spell to put the ones you’re not focusing on to sleep.
    • A nearby crate will have a Bio Sphere to heal your party at the next save
    • In the next room, after the save, go NE back to the Decoder door
  • Go back to the beginning of the area for a boss

Elsa

  • NE out, S to the robot behind the bar
    • In the S circle room, examine the middle of the sofa for a key
    • Around the perimeter of the hall you’ll get an email if you invested earlier. Downloading will let give you a 10% discount in stores.
  • Take the W elevator down
  • NE down the ladder, SW examine the green monitor by the bridge to connect another bridge and head W to find a chest for Decoder 10
  • Back one room, SW , S, then NW room for scenes
    • Back one room, you can speak to the robot in the middle to upgrade you AWGS if you want.
    • Go a little S to Tony and agree to help.
  • Head back to the top floor
    • 2nd circular room on the bottom, run around table for an email.
    • S to the restaurant will give you another email
  • Can go to the save point with the EVS on it. Open the UMN menu and start the EVS to go back to Kosmos Simulator to use the Decoder 10
  • Head back to the bridge for a scene and talk to Matthew to get the map for Tony
  • Go to the save for another investment email, invest in Venture Link for future money back and discount on AGWS shops
    • Return the map to Tony
  • Start back up, except, instead of going up the ladder go NW and to the tip to examine the monitor
    • While heading down you’ll receive another email, answer the Cargo seems suspicious
  • Return to the bridge

U-Tic Invasion

  • Make your way back down the ladder downstairs
  • Head back to the ladder
    • Chaos is now also part of the party, you can go back to the EVS simulators if you wanted to grind anyone, though there’s not really a great area to go to.
    • Chaos comes with a good party healing ether
    • Shion can also learn a party heal if you evolve Medica into Analyze and into Medica All
    • If you get Ziggy to lv 15 he can learn a Tech that hits all enemies, but can only be put to T+T
    • Only characters in battle receive EXP, EP, TP, SP
    • The droids are good for making some money as their drops sell for 400G+
  • Head down to the room below the AWGS hanger for a boss
  • Walk around to each room on the ship, make your way to the catapult bay again for an email towards the top, invest in Vector
    • Make your way S to the room before the AGWS hanger for a return investment email giving a discount in AWGS shops
  • When ready, head back to Cabin 2, the S sphere room, to rest.

U-Tic Battleship

  • You can’t customize anything on Jr. except his stats right now. Jr. is the only character who gets a physical “All enemies” tech that’s stronger than his ether based one. So focus on physical attack with him.
  • Head E and above bottom red line is a generator to destroy
  • NE to second generator
  • Around to further NE for red button
  • S to SE around to red button to open dor
  • Head E to the hall with multiple rooms.
    • Destroy connecting generators to NE room to use Decoder 11
  • Head S and around to SE to the first door on the right to the red button
  • Head S to both rooms at the end of the hall for 2 card keys
    • Head back to NE and open the E door for Decoder 16
  • Head back to the beginning of the area to the NW room and use the card key to open the door
  • Continue N to the next room flashing monitor to a boss

Dock Colony

  • Leave the bridge and head down to the Ziggy’s room, to the right of the AWGS hangar.
    • Should receive an email almost immediately allowing Kos Mos a new Tech
  • Head back up and take the NW exit near the bridge door to outside
  • 2nd door on the left leads to a shop with good equipment upgrades for everyone
    • Make sure to grab 1 of each accessory
  • Back up and head S for a scene
    • Can head to the clinic for an email
  •  Outside head SW for another scene
  • Back on the ship, you’ll immediately get an email, heading back to the elevator will give you another that you can download for a weapon for Kos Mos.
  • Head to the bridge and talk to Mathews

Cathedral Ship

  • There will be a decent difficulty jump in this area
    • If you focused some SP on getting Rare +10 from the Theif’s Gloves, you shouldn’t have an issue recovering since all Gnosis drop EP recovery items
  • NE continue to a scene
    • The flies in this area absorb lightning damage
    • If you still have the Nightwalker helmet, extract Sleep Guard from it
    • Sleep and Poison Guard is good for this whole area
  • Continue E, go NE to bring the elevator down to SE exit
    • Upstairs, have Momo as the party leader and examine the trashcan at the top of the stairs
  • NE to exit, NE into the building, NE again for a Decoder 15
  • Head NW and around W to an elevator to a treasure room
    • This is a good room for EXP since the unicorns drop quite a bit. Especially the one on the right who will continue summoning the giants if you don’t kill both.
    • The unicorns can also drop a horn that sells for 500G
    • Just a recap on “All Enemies” techs
      • Shion learns an Ether based at lv 30
      • Ziggy learns a fire Ether based at lv 15
      • Ziggy learns a lightning Ether based at lv 26
      • Momo learns a Physical based at lv 20
      • Momo learns an Ether based at lv 24
      • Chaos learns an Ether based at lv 20
      • Chaos learns an ice Ether based at lv 25
        • Kos Mos won’t learn one until you get an email allowing her to later
  • Continue W and SW to the guarded chest for Decoder 9
  • Head N to the tower, N inside,  destroy the barriers by the elevator and head NE
  • NE around to destroy another block on the elevator and press the switch
  • NW around to destroy another block and up the ladder for more blocks
    • E leads to a segment door you can open
  • Head back to 1F and into the elevator
  • Go to the center and elevator down to a boss

Durandal

  • Head W for an email about the Cathedral, continue W for an investment’s return email. Download the plugin for a discount on Mech accessories
    • Take the train to the Residential Area, far NE room for shop for new equipment
    • Take the train to the Hangar and straight E into the next room for an investment email, invest in Alkimia
  • Take the train to the Park for Momo
    • Upon exiting the room will be a return investment’s email
  • Take the train to the Residential Area, rest in the SW room
  • Take the train to the Dock, NE corner talk to Jr., he will officially join your party
    • Jr. learns a physical based “All Enemies” tech at lv 15
    • Jr. learns an Ether based tech at lv 24
    • Jr. learns another physical based tech at lv 30
    • Make Jr. the party leader, head back to the residential area NE corner in the shop room and examine the closet
      • It’s an optional difficult fight, but I had transferred Medica All to all of my characters, so it was dramatically easier. About halfway through his HP he will say for only Jr. to attack, but you can still attack with the others and get weakly countered.
    • For defeating him you get a swimsuit (Increase TP earned +25%), Soul Rhapsody (Jr.’s strongest single target), and the Ether that will summon him in battle
    • Don’t forget to go back to the Woglinde Simulator to open Segment door 16
  • Once ready, head to the dock and enter the NE ship

Kukai Foundation

  • You’ll almost immediately receive and email, respond that she’s on the Durandal
  • E to world map, S to AWGS shop, W down the stairs
    • Talk to the old man, exit and re-enter for next scene
    • Talk to the old man, run around the area destroying all the garbage for a new Ether for Shion
    • Back to the world map, head to the sector in the middle
      • Head W to the next area, up the immediate stairs to the first door
        • Inside destroy the boxes in the right corner but be careful not to break the doll
        • Talk to it to be told to talk to Tom in the dock colony
      • Head back to the Durandal and at the SE corner of the dock will be Matthews to take you to the Dock Colony
        • In the top left room you can talk to the little girl by the vase to give the flower seeds from the Cathedral mall
        • In the room where the shop is is the little boy Tom
      • Go back to the purple toy and ask for a “Great Story” to be told where Decoder 1 is
  • Rest at the Inn in the sectors and head for the Durandal
    • Take the train to the park to find the Decoder in the SE corner
  • Go back to the Elsa and speak to Allen

Making an Escape

  • Far NE room to reclaim equipment
  • Far SW room, closet door for a key
  • Take train to Hangar to open the armory for Decoder 5
    • If you want to grind points at all, the Isolation Area is the best spot. Has 3 soldiers close to each other and a room you can go in and out of to respawn
    • If you have 3 members with “All Enemies” tech you can easily always get the bonus. Almost as good as the AWGS at the beginning of Woglinde
  • Head for the dock
  • SW is a secret path to go around and inside
  • Head to Kos Mos lab

Encephalon Miltia

  • Search lights are basically enemy fights, SE to exit
  • Head N, SE, SE and around, ignore the first pot hole and go for NW corner next to the woman.
    • If you talk to the woman, these types of enemies need to be healed to be killed
    • Continue down the path for 2 red lights and a segment door
    • This gives you the Double Buster which allows you to do a shortcut tech with equipped S+S or T+T . This depends on which you press first in the S+O+O and T+O+O as well as you having 6 AP
  • Go back to the manhole skipped, halfway through grab the red button, NE to exit
  • SW to stairs,  run around the debris at the bottom of the stairs to the room in the NE to a segment door for an angel ring halfing EP cost
  • SW esculator, onto the tracks to E exit
  • SE around to NE exit, follow path to left ladder to Decoder 12, E Ladder out
  • Continue E, make way to SE
    • After watching the bunny, head  W and across the river  to go collect a can of carrot juice
    • Go back and place the can on the stump, try to get into the house before he does to get Decoder 3
  • Head NE and E into the church
  • Speak to Feb to fully heal before opening the door to a boss

Kukai Invasion

  • Start to head to the train to get an email for a new weapon for Kos Mos and, finally, her “All Enemies” tech that is Ether based
  • Some Sidequests quick:
    • Head back to Elsa Bridge to talk to Mathew to go to the Dock Colony
    • Talk to the woman outside the clinic 3 times
    • Go inside and talk to the little girl you gave the flower seeds to
    • Head back to Kukai Sectors to the far W last staircase up to a door with a blue canopy over the door.
    • In the back by the bookcases will be segment door 3
    • In the room before upstairs will be a white tux on the wall with the fish detector
    • Back outside, head to the far right to the Ironman bar.
    • Outside the door turn the switch on the left to bring out an awning
    • Inside, in the SW corner talk to the woman in light purple about an engagement ring
    • Head to the private beach and enter the water to start fishing, just examine every green npc marker on the map till the fish gives you the ring
    • Return to the woman and give her the ring for Decoder 8
    • Return to the Elsa B2 SW segment door
    • Return to Kukai, AWGS shop area to the scientist to turn in the 2 robot legs for a new ether
  • Once ready, head to the Ironman bar and talk to Allen on the E side
  • Head back to Kukai, head to the sectors where you’ll need to save 13 citizens
  • Iron Man bar for a man behind the cutouts on the E side
  • Next building shop area, talk to the man on the floor and W to safe, password 1028
  • NE upstairs, far E to red button to open gate to chest in Iron Man bar
  • Back and up the ladder to fall SW into he gate area for another man
    • Back to the roof, for E is segment door 1
    • Fall to the balcony and head E into a room, if you switch Momo to be the lead you can fight a boss similar to Jr.’s closet Joe. She doesn’t do a dramatic amount of damage, but does cause a lot of status affects and can send party members to the backrow. But you can defeat her for a weapon for Momo (Casts slow on Gnosis) and the Tech Dark Sceptor, which transforms Gnosis into items when defeated with
    • Back to the roof, head far W to the hole in the wall to Decoder 13
  • Back to Iron Man bar for a man hiding in the boxes in NW corner
  • Head W to next area to immediately save the man on the statue
  • Head up the left ladder to the top, go NE all the way around to the bottom and destroy the crate before the purple doll to save the couple
  • Back up to NE door, talk to the man, E around to yellow switch in the middle of the room
    • The Larvae here are very annoying, after about 150dmg they transform into Larvae Face that have about 300 HP. Try to transfer Medica from Shion to 3 characters to kill more easily
  • NE upstairs to find the cat, who counts as a person to save
  • Destroy the door to E for a boy behind the wall
  • Don’t slide down the nearby ramp, go W to the ladder and down it to a woman
  • Head back upstairs and SE to the door, follow the path till you’re back to the ladder.
  • Run down the ramp and press the red button, go to the center room to save the man
  • Head back outside to the NE door again, take the NW exit this time and follow to the final citizen
    • If you need an easy place to get some TP fast, the E room from the ladder has a bulky Gnosis that drops pretty good TP and items
  • Head for the exit of the sectors for a boss
  • Head back for the Durandal, immediately go back to where Momo was, then back to the Durandal’s train
  • Down the elevator for 2 more emails for Kos Mos
  • Return to the Elsa, the shop has been updated for new armor
    • Can also go back to the Cathedral ship for Segment Door 13
  • When ready talk to Mathews

Song of Nephilim

  • W to the elevator, the number of boxes destroyed determines the floor
  • 6 boxes, SW corner exit to a switch
    • 12 boxes, SW corner for Decoder 14
  • 15 boxes, NE exit to next tower
  • E room, make Momo the party leader to examine the middle of the wall for a new Ether and Tech
  • N room for another accessory, you should finally have enough to get to S. Lv 5 with someone to extract swimsuit
  • NW room to continue, down the ladder, SE ladder and NW to 2nd ladder for a mini boss blocking Decoder 2 and segment door 12
  • Go back to the ladder that we skipped
  • NE room to switch
  • Back in the hall take both other doors to break the yellow cylinders leading to a boss
  • Continue forward to red switch, SW elevator up to next tower
    • Be careful, enemies can cause instant death in this area
  • W and down the ladder, W destroy blocks to make the bridge come down
  • Down the ladder again and repeat, cross and go up the ladder
  • Destroy the blocks to go across, go up again, E and jump down to the blocked area for Decoder 17
  • Now go back to the left ladder and go down to get to the next room
  • Shoot the pillars to a specific amount of segments
    • Blue shoot 3
    • Red shoot 4
    • Green shoot 1
  • Go outside to switch and make way back up to the top of the tower and final bridge to 3 bosses
  • Leave the area through S door
  • Go down the elevator and receive 2 emails for Kos Mos final Tech and payment for finding the hacker
  • Elsa store has been updated again
    • Go down to the Catapult Bay for segment door 14
    • Talk to Mathews and go to the Dock Colony to the basement of the AWGS shop for segment door 2
    • Return to the scientist in Kukai to turn in the final robo parts
      • Speak to the professor till he asks for his assistant
      • Head to the Iron Man Bar to find him for a new ether that can do max damage to everything. Sadly, it requires all of your WT points to equip and costs 60 EP.
  • Once ready, talk to Mathews in the Elsa to go to Prot Merkabah

Proto Merkabah

  • Outside the Elsa after the scene
    • Downstairs immediately to NW corner for accessory
  • Back up and go around to NW corner
  • E to ladder down
  • W and press yellow 2 button and yellow 1 button
  • N press yellow 4 button and up the middle ramp
  • Head to NE elevator
  • Upstairs, W door, N door examine screens
  • Repeat up another floor
  • Repeat again up another floor
  • Up the next floor and go around W to back down a floor. Inside this room for segment door 17 with Jr.’s best weapon
  • Go down another floor and press the switch towards the middle
  • Go back to the top floor and down the new passage way
  • Head W and drop down to a boss, he will nullify Beam attacks, so plan Techs accordingly
    • You’ll receive Decoder 6
  • W up the ladder to the next area
    • NE around circle to destroyable object down the ladder to W last segment door
  • Back up, head N and E to next room
  • N room for a scene
  • SE down to elevator and the final save
  • W take the elevator down for a series of fights.
    • You can go back up and save and come down again without having to fight in the future
    • Make sure to block Confusion
  • Follow the path to a boss and then the Albedo and the final boss. Albedo is way harder than the final boss. Don’t be afraid to use the Kaiser on him to one shot

That’s all. Good luck!

Volodymyr Azimoff
About Volodymyr Azimoff 493 Articles
Being a big gaming fan, I believe that I have a lot to share with other gamers. I got my first official job in the game industry in 2005 and continue to develop there. It's a true blessing when your passion, hobby, and job combine into something one. My favorite console is the Nintendo Switch. I think you can all guess why. Because I just bought a Steam Deck. I love playing on PC, but my main love for me will always be Xbox. Anyway, it's complicated and simple at the same time. After all, I'm back in the days of the ZX Spectrum (1994)…

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